According to the Centers for Disease Control and Prevention, 6.7 million women (around 10.9%) in the United States between the ages of 15 and 44 suffer from impaired fecundity, or the ability to become pregnant and carry a baby to term. See Chandra A, Copen C E, Stephen E H. Infertility and impaired fecundity in the United States, 1982-2010: Data from the National Survey of Family Growth. National health statistics reports; no 67. Hyattsville, Md.: National Center for Health Statistics, 2013. A variety of factors such as endometriosis, high rates of aneuploid embryos, and polycystic ovary syndrome (PCOS) can contribute to impaired fecundity and understanding these causes on a case-by-case basis can help inform treatment decisions.
Endometriosis affects 10% to 15% of reproductive-age women. Symptoms of endometriosis may include infertility, chronic pelvic pain, irregular uterine bleeding, dysmenorrhea, and/or dyspareunia. Endometriosis is characterized by the abnormal growth of endometrial tissue, which normally lines the inside of one's uterus, on the outside of one's uterus. The displaced endometrial tissue may spread to one's ovaries, bowels, or pelvic tissue, and, in some cases, continues to act like normal intrauterine endometrial tissue during one's uterine cycle—by thickening, breaking down, and bleeding. The uterine cycle is regulated by hormones and has three major phases: the menstrual phase, the proliferative phase, and the secretory phase. The secretory phase is often further broken down into the early secretory stage, mid-secretory phase, and late secretory phase. Symptoms and severity vary by case along with the need for fertility treatment and the likelihood of success thereof.
The cause of endometriosis is unclear. The most widely-accepted explanation of endometriosis is retrograde menstruation. Retrograde menstruation occurs when menstrual blood containing endometrial cells flows back through the fallopian tubes and into the pelvic cavity, as opposed to flowing out the body. The endometrial cells present in the back flow are believed to stick to the pelvic walls and surfaces of the pelvic organs, where they continue to proliferate. Other proffered causes of endometriosis include embryonic cell growth, surgical scar implantation, endometrial cell transport, or an immune system disorder.
Expression studies for examining genes associated with endometriosis have provided further understanding of its etiology. For example, the expression studies have indicated that misregulation of a number of molecular pathways are associated with endometriosis. While expression studies offer insight as to what genes correlate with endometriosis, there has yet to be a consistent approach that allows one to characterize endometriosis or inform treatment of endometriosis based on expression levels and regulation patterns.
PCOS is a common endocrine system disorder with symptoms that may include irregular or no menstrual periods, heavy periods, excess body and facial hair, acne, pelvic pain, trouble getting pregnant, and patches of thick, darker, velvety skin. Impaired fecundity resulting from PCOS may be treated using a number of methods including diet adjustments, ovulation-inducing medications, surgical intervention, and assisted reproductive techniques such as in-vitro fertilization (IVF). For women with PCOS, like other disorders affecting fertility, success rates for these treatments vary on a case-by-case basis and are not generally predictable and understood.
Aneuploidy is the presence of an abnormal number of chromosomes in a cell. High aneuploidy rates are often associated with poor oocyte and embryo quality, both of which decrease with age and often lead to unviable embryos and, accordingly, impaired fecundity. While aneuploidy rates appears to increase with a woman's age, the association has not been well characterized and the ability to predict aneuploidy rates for a given individual would be useful in informing family planning and possible fertility treatment.
As noted, many cases of impaired fecundity are treatable, allowing a woman to become pregnant and carry a baby to term. Some methods, such as IVF, can be expensive and painful while not necessarily producing the desired outcome. Accordingly, providing an accurate picture of an individual patient's likelihood of success with a given treatment method and equipping the patient to maximize that likelihood is extremely important before undertaking a treatment regimen.